An experimental investigation into the effects of near-surface operation on the wave-making resistance of SSK type submarines

An experimental investigation into the wave making resistance of an appended submarine operating near the free surface is described. Resistance measurements on a 1.556m model of the DARPA SUBOFF submarine were conducted in the Australian Maritime College towing tank in Launceston Tasmania. Two model configurations, bare hull with and without the sail, were towed in a straight line at zero angle of incidence for a range of depths and speeds. The results show increased resistance for both configurations at shallow depths when compared to the deep water value. The increase in resistance is due to the energy required by the body to generate gravity waves on the free surface (wave making). The interaction of the various hull-borne wave systems causes the increase in resistance to be highly dependent on Froude number. For deep water conditions the measured increase in resistance due to the sail agrees well with published estimates of 8 percent for similar configurations. The wave making resistance characteristics of the SUBOFF model indicates that for full-scale shallow water operations there are Froude number regions that are favourable in the context of propulsive power requirements.